1. Field of the Invention
The present invention relates to fermentation vessels and closure devices for such vessels. More particularly, the present invention concerns fermentation vessels and specifically to fermentation vessels having closure devices which permit easy access to the vessel contents and also allow free exchange of gases between the contents and the ambient atmosphere.
2. Background of the Art
Fermentation processes, particularly cell or tissue culture procedures, are employed in a wide variety of research activities ranging from textiles to pharmaceuticals. Biotechnology research makes extensive use of fermentation procedures, which in general involve growth of a single purified strain of micro-organism with a goal of obtaining more cells or purifying the byproducts. The isolation of pure strains of microorganisms is a detailed process involving many steps. A newly identified colony of a particular microorganism is first transferred from a petri dish culture to a separate vessel containing appropriate nutrients. This microorganism is typically transferred several times to a new petri dish or a culture tube until the culture is free of contamination by other undesired strains of microorganisms. After purification of the strain, one needs to study the nature of this newly isolated strain of microorganism. For this purpose, one needs to grow it in a selected medium. The medium is inoculated with the microorganisms and placed in an incubator with a rotary shaker at a suitable temperature and for a period of time sufficient to permit growth of the microorganism culture. New nutrients or chemicals are added to the actively growing culture to impose selection pressure, or the new microorganism is sampled many times through the growth period for analysis and the consumed quantity of the nutrient medium is replenished. These operations require inoculation of a culture in the vessel by means of a sterile inoculation loop inserted through the mouth of the culture vessel so as to touch the medium inside. Similarly, sampling of the contents during the growth period requires introduction of sterile sampling devices into the active culture. Good laboratory practice dictates that all apparatus involved with a procedure viz. the closure, the vessels the inoculation loop and the samplers must be sterile to avoid contamination by exogenous microorganisms. All of these operations according to known practice, require manipulation of the vessel, the closure and a transfer loop or pipette with interchanging of functions involving both of the worker's hands. This process is cumbersome and needs lot of experience to accomplish without error, particularly when one has to handle multiple vessels. The vessel is typically in the form of a test tube or flask.
With the prior art type of vessel, the worker has to perform the following series of operations for each vessel:
(i) lift the vessel from the rack with a first hand; PA1 (ii) remove the cap with second hand; PA1 (iii) keep the cap somewhere in the work area which itself must be kept sterile; PA1 (iv) pick up the inoculation or sampling device with a second hand: PA1 (v) perform inoculation or sampling, as the case may be: PA1 (vi) set the sampling device down to make second hand free; PA1 (vii) look for the same cap to avoid cross contamination; PA1 (viii) replace the cap carefully; and PA1 (ix) place the vessel back in the rack. PA1 (i) lift the vessel from the rack with a first hand (actually this is not necessary in some applications e.g. in inoculation only); PA1 (ii) open the lid of the closure using thumb or pointer finger of the first hand (the closure need not be removed and cannot be removed when it is molded as one piece with the vessel); PA1 (iii) pick up the inoculation or sampling device with the second hand: PA1 (iv) perform the inoculation or sampling; and PA1 (v) close the vessel with the finger of the first hand.
The vast majority of microorganisms useful in commercial viable fermentation processes are aerobic microorganisms; that is, microorganisms which require oxygen to carry on their metabolic processes. In fact, the very purpose of shaking or stirring fermentation broths is to ensure effective mixing of air with the liquid culture medium. As a result, any closure device employed in the culturing of aerobic microorganisms must permit the passage of air into the vessel and the discharge of gaseous fermentation byproducts from the vessel while maintaining the sterility of the vessel contents.
In the past it has been the widespread practice to close the fermentation vessel with porous closures such as a sterile cotton plug or a synthetic material such as foamed polyethylene or styrene etc. More recently, stainless steel and plastic cap closures have become available which fit over the mouth of the fermentation vessel and permit the passage of gases into and out of the fermentation vessel. Examples of such closures are KIM-KAP closures and KAP-UTS plastic closures available from Owens-Illinois and BELLCO stainless steel closures available from Bellco Technology. These closures each have an internal diameter slightly larger than that of the neck of the fermentation vessel and fit snugly over the vessel mouth by means of fingers or ridges on the inside vertical walls of the closures. Small fins inside the closure prevent the top of the closure from seating against the top of the fermentation vessel, thus permitting the passage of gases into and out of the vessel while maintaining the sterility of the vessel contents.
A disadvantage of these prior art closures, whether of the porous plug type or the snug fitting cap closure type, is the need to completely detach the closure in order to gain access to the fermentation vessel contents. Each removal of the closure provides the potential for contamination of the vessel contents and requires flaming or other sterilization treatment of the vessel mouth and closure to ensure sterility which adds to the amount of work required of the laboratory technician per unit vessel. A further style of prior art closure for a fermentation vessel is disclosed in U.S. Pat. No. 5,116,758 to the present inventor for a FERMENTATION VESSEL CLOSURE. The prior '758 patent addresses certain of these problems, but leaves others unresolved.
Thus, there is a need in the fermentation art for efficient fermentation vessels and closure devices which not only permit easy and direct access to the fermentation vessel contents without the need to remove the closure device but also allow for gaseous exchange.
Therefore, it is the principal object of the invention to provide a one piece closure, all portions of the closure being integral with each other and which may be opened and closed with the hand holding the vessel typically in the form of a test tube or flask.
Another object of the invention is to provide a fermentation vessel which can be molded integrally with an easily opened and closed closure cap.
Another object is to provide a fermentation vessel having a closure which permits easy access to the vessel contents and allows gaseous exchange.
The foregoing and other objects will become apparent as the description proceeds.